Caption: Terraformed Mars. Computer artwork of the planet Mars with oceans of liquid water following a future terraforming. This process, which involves changing the climate so it is more habitable, would be carried out to allow humans to colonise the planet. Mars is currently a cold, desert world, with no liquid water. This artwork could also represent Mars in the past, when its atmosphere was thicker and warmer, and it had liquid water on its surface. On the surface, Valles Marineris, the largest canyon system on Mars, is at centre. The large flooded impact crater at lower right is the Argyre Planitia.